MISC DRUGs - Flashcards
where and how is alcohol absorbed?
small amiphatic molecule
can cross lipid bilaters with no transporter
20% absorbed from stomach, 80% small intestine via simple diffusion
Vd of ethanol?
0.6L/kg
describe the metabolism of alcohol
metabolised in the liver and gastric mucosa = 1st pass metabolism
acetate can be converted to acetylcoA and enter krebs
starts as 1st order and then rapidly to 0 order - 1unit/hr
10% is metabolised by CYP2E1 which is upregulated in chronic alchols
can be excreted unchanged by kidneys too
and exhaled
how is the level of alcohol in someone measured?
blood alcohol content = most reliable
mass of alchol per volume blood
breathalyser - quick and rapid test
urine alcohol - not v accurate
how does a breathalyser work?
original breathalysers are pottasium permanganate = change colour in presence of alcohol
modern uses fuel cells that oxidises ethanol
alcohol crosses pulmonary endothelium and vapourises and is exhaled
BAC correlatates with alveolar conc
what can give a false positive breathalyser test?
GORD , mouthwash
how are units calculated
1 unit = 10ml or pure alcohol
25ml of 40% = 1unit
1 glass of wine = 2 units
1 pint of beer = 3 units
recommended male and female alcohol intake?
women = 14 units/ week
men = 21 units/ week
why do women have a lower recommended alcohol intake than men?
lower body water content
slower enzyme pathways
receptor action of alcohol?
GABA A allosteric modulation
enhances glutamate activity
dopaminergic activity too
pharmacodynamics of alcohol?
ACUTE:
desirable effects - euphoria, mood elevation
CNS - poor judgement, discordination, can lead to sedation
A - aspiration risk and airway obstruction
B - resp depression
C - increased HR and arrhythmias , vasodilation
metabolic - hypoglycaemia, dehydration (ADH)
CHRONIC:
wernickes and korsakoff
CVS disease
liver disease - fatty liver, cirrhosis, varices, coagulopathy
pancreatitis
gastritis
what is the pathogenesis behind alcohol withdrawal?
with chronic use GABA downregulation and glutamate upregulation
so without alcohol brain becomes more excitable
hence withdrawal and tolerance develops
tremors, anxiety, insomnia
seizures
delirium tremens
what is wernickes and korsakoff?
secondary to thiamine deficiency due to malnutrition and malabsorption
wernickes = encephalopathy, gait ataxia, nystagmus
korsakoff = amnesia and confabulation
how is acute alcohol withdrawal managed?
pabrinex - B vitamin mixture to replace thiamine
withdrawal symptoms are scored - GMAWS
benzos given based on this
e.g. chlordiazepoxide, diazepam or lorazepam in liver disease
what screening tools for alcoholics are there?
CAGE - cut down, annoyed, guilt, eye opener (first thing you think in morning)
AUDIT questionaire
what is the role of disulfiram
inhibits aldehyde dehydrogenase, aldehyde builds up and causes unpleasent effects to reduce drinking.
what is fomepizole
Fomepizole is a medication used as an antidote in cases of poisoning from toxic alcohols, primarily ethylene glycol (found in antifreeze) and methanol.
inhibiting the enzyme alcohol dehydrogenase, which is responsible for metabolizing these toxic alcohols into harmful substances.
how do cannibinoids work?
contain THC which is the active ingredient with psychoactive effects.
bind cannabinoid receptors - stimulatory initially and then inhibitory
effects of cannabinoids
CNS - calmness, anxiety, sedation, dysphoria, psychosis
vasodilation
increased appeptie
effects of smoking - lung cancer, COPD
what are the effects of cocaine?
local anaesthetic agent with NA and serotonin reuptake inhibition causing euphoria
acute - tachycardia, euphoria, anxiety, HTN, vasospasm. risk of strokes, MI, seizures.
serotonin syndrome risk
pupil dilation
chronic - IHD and cardiomyopathy, nasal septum perforation
what anaesthetic considerations in someone with cocaine?
avoid sympathetic stimulants and serotonin drugs - ephedrine, pethidine, tramadol
how is acute intoxication with cocaine managed?
supportive care
may need intubating if reduced GCS
benzos - agitations and seizures
treat complications - nitrates for HTN
how do amphetamines work molecularly ?
stimulate the release of dopamine and serotonin causing excitemnet and euphoria
also inhibit MAO
what are the pharmacodynamic effects of amphetamines?
euphoria, excitement, energy
CVS - tachycardia and arrhythmias
metabolic - increase ADH and thirst
electrolytes - hyponatraemia - can lead to cererbral oedema
risk of serotonin syndrome